The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to signal processing circuits and more particularly to signal processing circuits for providing a fuze-on-jam capability in a target detecting device when in the presence of continuous wave or continuous wave noise jammer signals.
In known passive target detection systems carried by missiles that home on a target radar, (As for example, the target detecting device as shown and described in application Ser. No. 04/553,344 filed May 27, 1966 now U.S. Pat. No. 4,320,703 for Target Detecting Device by Erwin I. Abadie et al.) the signals received by the target detecting device from its antennas are the radar pulses transmitted by the target but appear as negative signals due to the antenna phasing. Upon close approach of the missile to the target the signal received by the antennas goes through a null at the critical angle of the antenna and reverses phase to produce a positive signal. The target detecting device is designed to prime a gate on the train of negative pulses and then to fire upon the first or second positive pulse received after the above phase reversal following antenna crossover. In the presence of continuous wave noise jammer signals, a negative bias signal with an a-c component is produced at the output of the detector stage of the target detecting device. This signal may be mistaken by the target detecting system electronics as a signal and premature firing may result. In the presence of a continuous wave radar only a direct current signal will be detected and no pulses will be present to initiate the firing circuit.
The present invention provides a modification of the prior target detection systems which will both protect the target detecting device from noise jammers and will provide fuzing capability on both noise jammers and continuous wave radars or continuous wave jammers.
The present invention provides a circuit which samples the negative or positive bias produced by the noise modulated CW signal and produces pulses of either positive or negative polarity as seen by the antenna. If negative pulses are produced, they will actuate the target detecting gate and guard circuit and after the missile has passed the critical angle of the antenna the phase change will produce a positive pulse which will then produce firing in the normal manner. Because of the manner in which the sampled output will be fed into the target detecting mixer circuit, there will be no interference with the normal operation of the target detecting device but an additional fuze-on-jam or CW capability is provided.
Accordingly, an object of the present invention is to provide a passive target detecting system which will fuze on jammer signals, continuous wave radar signals and target signals.